The invention relates to orthopedic splints or braces and, more particularly, to a hallux (big toe) valgus (abnormal angulation) brace.
FIG. 1 shows a foot afflicted with both a bunion (1) on the big toe (Hallux Valgus) and hammer toes (2) on the other four. These deformities can happen individually but they often happen together as shown. The terms “hallux valgus,” or “hallux abducto-valgus,” are the most commonly used medical terms associated with a bunion anomaly, where “hallux” refers to the great toe, “valgus” refers to the abnormal angulation of the great toe commonly associated with bunion anomalies, and “abductus/-o” refers to the abnormal drifting or inward leaning of the great toe towards the second toe, which is also commonly associated with bunions. Note that, “hallux abducto” refers to the great toe moving away from the body's midline, and ‘inward’ to the second toe.
In FIG. 1, the big toe has slid under the second toe and the second toe never contacts the ground. There are many shortcomings with the prior art devices designed to straighten out the big toe, to correct hammer toes, or remedy both. Most don't work or are unsuitable for daily use. That is, most prior art devices aim to immobilize the big toe in a straight out stiffness, which is uncomfortable. The big toe needs to flex.
To understand the problem, a review of the bones of the foot is necessary. FIG. 2 shows the dorsal surface of the bones of the foot. The bones are divided into three groups:—the tarsus (3), the metatarsus (4), and the phalanges (5). When the foot is at rest (no load) the metatarsus bones keep a narrow profile. As a human stands up, a load is slowly applied to the foot, and the metatarsus bones fan apart from their base at the tarsus to make the foot wider. A wider foot provides more stability and it has lower unit area stresses than a narrow foot. As the load increases from dynamic activities such as walking, running or jumping, the bones fan apart even farther again to increase stability, to reduce the unit area stresses and to reduce shock. During the acts of walking, running or jumping, it is important to note that when the foot is lifted off of the ground, it returns to its narrowest width only to widen again when the foot is bearing the entire weight of the body.
The knuckles are the joints of the toes. The knuckles (6) at the base of the toes are where the metatarsus and the phalanges connect, at the ball of the foot, and may be referred to as the 1st or major knuckles. The knuckles at mid-toe are known as the 2nd knuckles (62) and 3rd knuckles (63) respectively. The pivot axes of the major or 1st knuckles (6) do not form a straight line. The smaller toes's major knuckles (6) pivot on an axis that sweeps along a gentle arc. The pivot axis for the big toe's major knuckle (6) is stepped back quite a step from the gentle arc of the smaller toes.
FIG. 3 shows a cutaway of the side of the foot with the tarsus and the metatarsus bones positioned for standing (7). During walking or running the toes remain flat on the ground and the tarsus and metatarsus pivot upward as shown (8). As the foot is pivoting upward, each toe is flexing upward (relative the plane of the metatarsals) at the pivot axis where the toe connects with its metatarsal, namely, its major knuckle (6). Since the pivot axes for the major knuckles (6) are far from a straight line, this causes the toes to fan apart, which increases stability.
When humans sleep (approx. 8 hours a day), the feet have no load and little movement. The remainder of the time (16 hours a day) the foot might be in constant movement with continual cyclic loading. It is the basic movement of the foot and differential movement between the bones (as described above) that most treatment devices and methods can not accommodate.
Some rigid devices tie to the base of the foot and use a lever to pull the big toe outward (ie., out from under the second toe, so, inward relative the body's midline). Most of these don't flex with the foot or do not fit in a shoe. And many of these immobilize the big toe in a straight out stiffness.
There are other devices that use an elastic bandage or sock to pull the big toe outward. But the big toe will return inward as the foot flexes during walking because the elastic becomes slack.
FIG. 4 shows how a spacer (9) placed between toes can easily become displaced during walking. This can happen even if the spacer is in a sock or attached to an elastic band.
The devices that attempt to manipulate the big toe outward by using the other four toes as a base, restrict the movement and bending of all the toes. As each of the phalanges and metatarsals move according to its load, these devices can not keep the big toe in its desired (corrected) position. Some use a rigid rod that runs under the toes and prevents the toes from laying flat on the ground. Any attempt to tie the toes together in the proper spacing fails because each toe bends independently and their major knuckles/pivot points (6) are not aligned with each other nor with the big toe. Most devices don't work and if they do, the user will experience pain and have a difficult time getting his/her foot into a shoe, and then a difficult time walking.
What is needed is an improvement over the shortcomings of the prior art.